This program's objective is the delineation of the structural and functional relations between the isozymes of urease, and of the pharmacology of its hydroxamate inhibitors in relation to human disease and animal nutrition. Urease is perhaps the most suitable of all protein for correlative structure-function studies of association-dissociation phenomena, because of its catalytic potency, its wide variety of non-genetic isozymes, and their slow equilibria, which make feasible the discrete analysis of individually isolated forms. Aggregate-state studies will depend primarily on ultracentrifugation and gel electrophoresis, while conformation and denaturation will be assessed by UV spectrophotometry, circular dichroism, and chemical reactivity. Isolated isozymes will be compared by catalytic assay for differences in specific activity, pH-activity curves, substrate activity ratios, inhibition patterns, and inactivation rates; and labelled complexes will be sought. The functional division of thiol groups in the enzyme will be investigated by chemical modification; and comparative study of a purified bacterial urease should give some insight into the evolutionary development of the molecule. The urease polymers will also provide a useful tool for analyzing the theory and practice of gel electrophoresis. The aliphatic hydroxamates are potentially useful agents in the treatment of hepatic coma, uremia, and sepsis or urinary-tract infections with ureolytic bacteria; and for improving nitrogen retention in livestock maintained on non-protein-nitrogen diets. For these reasons the anatagonism of ureolysis by these compounds must be documented in vitro, by enzymatic assay, and in vivo, using C14-urea. Their toxicology and disposition in animals must also be evaluated. This program should result in a better understanding of association and dissociation of proteins, and may help to introduce a new group of drugs into clinical medicine. BIBLIOGRAPHIC REFERENCES: W.N. Fishbein, K. Nagarajan, and W. Scurzi, Structural classes of jackbean urease variants and their relation to a structural classification of isozymes, in Isozymes, I. Molecular Structure (C.L. Markert, ed.) Academic Press, New York, 1975, pp. 403-417.